<template>
  <ul class="list">
    <li class="item"  v-for="(item,index) of letters" :key="index"
     @click="handleLetterClick"
     @touchstart="handleTouchStart"
     @touchmove="handleTouchMove"
     @touchend="handleTouchEnd"
     :ref="item">
      {{ item }}
    </li>
  </ul>
</template>

<script>
export default {
  name: 'CityAlphabet',
  props: {
    cities: Object
  },
  computed:{
    letters(){
      const letters = []
      for (let i in this.cities){
        letters.push(i)
      }
      return letters 

    }
  },
  data(){
    return {
      touchStatus:false
    }
  },
  methods:{
    handleLetterClick(e){
      this.$emit('change',e.target.innerText)
    },
    handleTouchStart(){
      this.touchStatus = true
    },
    handleTouchMove(e){
      if(this.touchStatus){
        const startY = this.$refs['A'][0].offsetTop
        const touchY = e.touches[0].clientY - 79
        const index = Math.floor((touchY - startY) / 20)
        console.log(index)
        if (index >= 0 && index < this.letters.length) {
          this.$emit('change',this.letters[index])
        }
      }
    },
    handleTouchEnd(){
      this.touchStatus = false
    }
  }
}
</script>




<style lang="stylus" scoped>
  @import '~styles/varibles.styl'
  .list
    display: flex
    flex-direction: column
    justify-content: center
    position: absolute
    top: 1.58rem
    right: 0
    bottom: 0
    width: .4rem
    .item
      line-height: .4rem
      text-align: center
      color: $bgColor
</style>
